The production of quark-antiquark pairs along a color flux tube precedes the fragmentation of the tube. Because of local conservation laws, the production of a $q$-$\bar q$ pair will lead to correlations of adjacently produced mesons (mostly pions). Adjacently produced mesons however can be signalled by their rapidity difference $\Delta y$ falling within the window of $|\Delta y | $$\lesssim$$ 1/(dN/dy)$, on account of the space-time-rapidity ordering of produced mesons in a flux tube fragmentation. Therefore, the local conservation laws of momentum, charge, and flavor will lead to a suppression of angular correlation function $dN/(d\Delta \phi\, d\Delta y)$ for two mesons with opposite charges or strangeness on the near side at $(\Delta \phi, \Delta y)$$ \sim$0, but an enhanced correlation on the back-to-back, away side at $\Delta \phi$$\sim$$ \pi$, within the window of $|\Delta y |$$\lesssim$$ 1/(dN/dy)$. These properties can be used as signatures for the fragmentation of a color flux tube. The gross features of the signature of flux tube fragmentation for two oppositely charged mesons are qualitatively consistent with the STAR and NA61/SHINE angular correlation data for two hadrons with opposite charges in the low-$p_T$ region in high-energy $pp$ collisions.
Categories: hep-ph hep-ex nucl-th